
int f2(int n)
{
    int sum=0;
    while(n)
    {
        sum+=n%10;
        n/=10;
    }
    return sum;
}

int f(int n)
{
    if(n<10)
        return n;
    return f(n/10)+(n%10);

}
int g(int left,int right)
{
 int n=right-left+1;
 return n*(left+right)/2;
}
int main()
{

    printf("%d\n",g(1,100)==5050);
}
